# Perfectly balanced

Given a string containing only lowercase letters, find whether every letter that appears in the string appears the same number of times. Don't forget to handle the empty string ("") correctly!

## Examples
```text
balanced_bonus("xxxyyyzzz") => true
balanced_bonus("abccbaabccba") => true
balanced_bonus("xxxyyyzzzz") => false
balanced_bonus("abcdefghijklmnopqrstuvwxyz") => true
balanced_bonus("pqq") => false
balanced_bonus("fdedfdeffeddefeeeefddf") => false
balanced_bonus("www") => true
balanced_bonus("x") => true
balanced_bonus("") => true
```